Loud speaker



sgpf. 1,1931'.

C. BLIEBERGER LOUD SPEAKER Filed Jan. 18, 1950 3 Sheets-Sheet l lllllllnmmun111ml/l C. BLIEBERGER Sept. 1, 199,1.

LOUD SPEAKER Filed Jan. 18, 1930 3 Sheets-Sheet 2 lN-VENTOR Sept. l, 1931. C. BLIEBERGER 1,821,373

LOUD SPEAKER Filed Jan. 18, 1930 3 Sheets-Sheet 5 WWII "WWII/1u I INVENTOR ATTCRNEY Patented Sept. 1, 1931 PATENT OFFICE UNITI-:D STATES CHARLES BLIEBERGER, OF NEW YORK, N. Y.

LOUD SPEAKER Application filed January 18, 1930. Serial No. 421,644.

The present invention relates broadly to acoustics and more especially to a sound producing apparatus comprising a loud speaker 'for radios, address systems, phonographs,

etc. l y

It i-s particularly desirable in loud speaking apparatus to provide constructions adaptable tor responding, under power impulses, to a large range ot sound waves, and

:1o also to be capable of response to complex sound waves such as voice, etc., without distortion.

One of the diiiicultie-s in producing air waves mechanically is to provide a mechanism which does not possess a deiinite normal rate of vibration and thereby tend to over-amplify air waves which correspond to the Zone ot normal vibrations ot the mechanical device itself.

The present invention overcomes the ditficultiesA of the known art by providing a mechanical structure adaptable to be electrically or otherwise power o erated and whereby a fidelity of tone repro uction is ob- ,gfg tained because of the uniform response to the air wave produced throughout a very wide range of tones. The desirable etlects of the present inventionV appear to be brought about by providing and suitably mounting a diaphragm member capable of response to a wide range ot tones and wherein the diaphragmis equally responsive to the tones in a Wide range without being over responsive to any particular zone of waves. The diaphragm in the present case is therefore constructed in such manner as to obviate its individualcharacteristic as a whole to any particular tone or harmonic ot that tone. One tormof the present invention comprises the production ota diaphragm ot substantially circular shape with a portion ot' the diaphragm being relatively thick and tapering from the thick port-ion to an edge of uniform thickness. This thick portion is offset 4Q an ineommensurate distance from the center ot the diaphragm so that it obviates undue harmonic vibrations, and since the thickness ot' the diaphragm tapers in all directions from this high point to the edge ot uniform thickness, sections cut through the diaphragm in various directions respond to waves of diiterent frequencies and vibrate wedge shaped portions ot the diaphragm having their thick base adjacent the thick point ot' the diaphragm and their points ot a ma uniform thickness, due to the uniformity ot thickness of the edge of the diaphragm. By this construction, it will be observed that portions ot the diaphragm representing the longest distance from the thick spot to the edge will respond to one group ot air vibrations and that the portion ot the diaphragm determined by the shortest distance between the thick spot and the edge will respond at another zone of vibrations and that other parts ot the diaphragm between these two maximum dimensions will respond to all intermediate tones. This result is brought about by the combination of the offset center and the varying thickness of the diaphragm. It is further brought about by dampening ot the operating` mechanism for the diaphragm. For example, the power communicating rod is preferably covered at suitable intervals with dampening material such as rubber tub- 75 ing, which prevents any extraneous vibration being established in the operating rod, and the point of connection between the operating rod and the diaphragm itselt` is preferably a yielding connection such as a leather pad or some other resilient substance. The diaphragm in accordance with the present invention may be made ot various materials but experimentation has shown that diaphragms made of wood are particularly elfec- 85 tive, and some ot the best results have been obtained by making the diaphragms of hard ma le.

hile the present invention is not limited to definite sized parts, experiments have 90 shown that a diaphragm in accordance with the following dimensions produce very satisfactory results. A board of hard maple '-,ths of an inch in thickness cut away at the c-enter to provide a diaphragm 15 inches in diameter and with the edges of the diaphragm gnd of an inch thick. The thick point in the diaphragm has a thickness of gggnds of an inch Vand is located on a center line of the diaphragm 4% inches from one side and 10% inches from the other side. These proportions are such that the results are very satisfactory. After the diaphragm has been cut in accordance with the dimensions specified and carefully smoothed and polished,.it is then preferably treated by being shellacked or varnished on both sides to obviate weather effects and also to lill the wood pores.

Diaphragms have been made of many other' materials other than wood and also in various different sizes, so that it is to be understood that the above disclosure is illustrative and not in the limiting sense.

The present invention may be embodied in structures other than those herewith specilically disclosed and therefore it is to be understood that the disclosure is the preferred form in accordance with the patent laws and is not to be considered in the limiting sense.

Referring now to the drawings, Fig. 1 illustrates a diaphragm plate in accordance with the present invention. l Fig. 2 is a sectional view on line F ig. 1.

Fi 3 illustrates the diaphragm mounted in a frame. v

Fig. 4 is a vertical section through the construction shown in Fig. 3 and illustrating the operatin g mechanism.

Fig. 5 is a detail of the upper portion of Fig. 3.

Fig. 6 is a plan view of a diaphragm in accordance with the present invention.

Fig'. '7 is a view on line 7 -7 of Fig. 6.

Fig. 8 is a cross-section through Fig. 6 on line 8 8.

Fig. 9 is a cross section on line 9 9 of Fig. G.

Referring now to the drawings. The diaphragm 1 is preferably constructed by cutting away one side of a wooden slab or board in such manner as to provide a thin vibratory diaphragm having a thick portion 4 from which the diaphragm tapers to an edOe 5 of substantially uniform thickness. Prefrably, though not necessarily, the opposite side 6 of the diaphragm is a plain surface. The thick portion of both the diaphragm and the edges are exaggerated in the drawings in order to be able to illustrate these features.

As will be observed from Figs. 6, 7, 8, and 9, the thick portion 4 of the diaphragm is odset from the center of the diaphragm, and as measured along the diameter D which passes through the center of the thick portion 4 and the center of the diaphragm, this thick portion 4 is offset an incommensurate distance from the center of the diaphragm. This thick spot divides the total surface of the diaphragm in such manner as to prevent the tendency to produce harmonic vibrations other than those desired and also. divides the diaphragm in such manner as to provide a large number of incommensurate sectorial lines passing through the thick spot 4. This renders the diaphragm particularly sympathetic to all wave lengths between those which are in harmony with the shortest portion of the diaphragm between the thick portion 4 and the edge 5, and those which are in sympathy with the longest distance between the thick spot 4 and the edge 5 of the diaphragm. This sympathetic relationship is local to various parts of the diaphragm depending upon the particular wave length which is being reproduced.

lIiile the diaphragm is preferably made of wood, such as hard maple, which has been suitably varnished, the diaphragm may be also made of other materials such as pressed paper, liber board, metal, etc.

A preferred mounting for the diaphragm is to mount the frame portion 7 of the diaphragm in a front board which preferably is made of two supporting members 8 and 9, which are cut away at 10 and 11 to provide unobstructed openings of the size of the diaphragm 1. Each of the supporting members 8 and 9 are recessed to receive substantially one half of the thickness of the frame 7 of the diaphragm and the diaphragm is tightly clamped between the supporting members 8 and 9, so that these members comprise front boards which rigidly support the diaphragm 1 whereby the air vibrations are established by the diaphragm itself. Preferably, baiiles 12, 14, 15 and 16 are secured to the front board and are open at the back with the exception of a unit support 17 which eX- tends between the bafiles 12 and 14. These baflies may comprise a wooden framework, preferably dove-tailed at the corners to form an open backwardly extending frame which screens the frontl of the diaphragm 1 from the back thereof inA such manner that the air waves from the front of the diaphragm are not distorted byinterference to the air waves from the back thereof.

Where the present invention is utilized as a telephonic loud speaker with a radio or a loud speaker address system or the like, it preferably is operated by an electromagnetic unit such as is common in the art and which is carried upon the unit support 17. The connection between the unit 18 and the diaphragm 1 preferably comprises a small rod 19 which bears against a resilient pad 20 of leather or the like. Preferably, the contact between the driving rod 19 and the dia` phragm 1 is by lateral pressure of the end of the rod-19 against the resilient pad 20.

However, there may be occasions where it is desirable to permanently attach and anchor the rod l9 to the diaphragm. The application of power through the rod 19 is preferably directly over the thick spot 4 of the diaphragm so that this spot becomes the initial point of vibration of the diaphragm. In order to obviate any extraneous vibration being set up in the rod 19, the rod is dampened by means of dampening members 21 which may comprise short separate sections of rubber tubing of sufficiently small diameter to be expanded slightly when the rod 19 is telescoped through these sections.

rIhe device in accordance with the present invention as herein disclosed faithfully reproduces complex sounds through an extremely large range,and does not tend to distort reproduced sound by over-amplification of any particular band of sound waves, and neither does it distort the sound waves because of extraneous waves introduced through the vibration of the connecting parts.

While the diaphragm is disclosed as being circular in form, it is to be understood that the form herein shown is merely illustrative and that other shapes may be used with equal facility.

Having described my invention, I claim 1. An acoustical diaphragm comprising a resonating member having a. substantially circular edge of substantially uniform thickness, a thick zone tapering in all directions toward said edge, said thick zone being located on a diameter of said diaphragm and offset from the center of said diaphragm so that the distance from said thick zone measured along said diameter to one edge is incommensurate relative to the distance from said zone along said diameter to the other edge.

2. In an acoustical device, a diaphragm comprising a resonating member having a substantially circular edge of substantially uniform thickness, a thick zone tapering in all directions toward said edge, said thick zone being located on a diameter of said diaphragm and offset from the center of said diaphragm so that the distance from said thick zone measured along said diameter to one edge is incommensurate relative to the distance from said zone along said diameter to the other edge, and driving means operative to deliver power to said thick zone to vibrate said diaphragm.

3. An acoustic diaphragm comprising a relatively thick slab provided with a circular depression, the edges of said diaphragm being substantially uniform in thickness and with a thickened zone offset from the center of said depression and sloping in all directions to the edge thereof.

4. In an acoustic diaphragm comprising a vrelatively thick slab provided with a circular depression, the edges of said diaphragm being substantially uniform in thickness and with a thickened zone offset from the cen ter of said depression and sloping in all directions to the edge thereof, and driving means operative on said thickened zone.

5. An acoustic diaphragm comprising a slab having a thick portion and a depression therein forming a thin vibratory member supported by the thick portion of said slab.

6. VIn an acoustic device, a diaphragm comprisifng a slab having a thick portion and a depression therein forming a thin vibratory member supported by the thick portion of said slab, and driving means to vibrate said thin vibratory member.

7. An acoustical diaphragm comprising a circular member with a substantially uniformly thick edge, and with a thick zone tapering toward said edge; the proportions of said diaphragm bei-ng diameter fifteen units, and the thick zone being oifset three units from the center of said diaphragm.

8. An acoustical diaphragm comprising a I circular member with a substantially uniformly thick edge, and with a thick zone tapering toward said edge; the proportions of said diaphragm being diameter fifteen units, the thick zone being offset three units from the center of said diaphragm, the thickness of the thick zone being substantially three times the thickness of said edge.

9. In an acoustical device, a diaphragm comprising a slab provided with a circular depression, an anchoring frame having openings substantially the size of said depressed portion and adapted to clamp said slab with the depressed portion thereof exposed, means to support said anchoring frame, and driving means for vibrating said depressed portion of said slab.

10. In an acoustical device, a diaphragm comprising a slab provided with a circular depression, an anchoring frame covering portions of both sides of said slab and having openings substantially the size of said depressed portion and adapted to clamp said slab with the depressed portion thereof eX- posed, means comprising a baille member to support said anchoring frame, and driving means for vibrating said depressed portion of said slab.

11. An acoustical device comprising a slab having a thick portion and a thin portion with a thin portion comprising a resonating diaphragm, anchoring means for supporting the thick portions of said slab against vibration, means to support said anchoring means, and driving means to vibrate said thin portion.

12. An acoustical device comprising a slab having a thick portion and a t-hin portion with the thin portion comprising a reson ating diaphragm with the mass of said diaphragm non-uniformly disposed relative to the geometric oenter of the diaphragm, anchoring means for supporting the thick vportions of said slab against vibratiommeans to support said anchoring means, and driving means to vibrate said thin portion.

13. In an acoustical device, a diaphragm, power means for operating said diaphragm, said power means comprising an operating pin, and vibration dampening means to prevent transverse vibration Vto said pin.

Y CHARLES BLIEBERGER. 

